# Патент USA US3088072

код для вставкиApril 30, 1963 A. A. HUDIMAC 3,088,062 ELECTROMECHANICAL VIBRATORY FORCE SUPPRESSOR AND INDICATOR Filed Feb. 10, 1956 7 Sheets-Sheet l {32 Eff’ Fr F/'g. /0 2b Fig lb I INVENTOR. ALBERT A. HUD/MAC A TTORNEYS April 30, 1963 A. A. HUDlMAC 3,088,062 ELECTROMECHANICAL VIBRATORY FORCE SUPPRESSOR AND INDICATOR Filed Feb. 10, 1956 7 Sheets-Sheet 2 32 / 28 lllll| I \\\\\\\\\\\\\\\\\\\\\\\ \\ \22 34 24 s||||| /2 11H Fig. 2 TO TUNING INDlCATOR A F 'g. F 4 _ INVENTOR. ALBERT 4. HUD/MAC 8Y5: i g. Jam?‘ 2- M A T TORNEYS April 30, 1963 3,088,062 A. A. HUDIMAC ELECTROMECHANICAL VIBRATORY FORCE SUPPRESSOR AND INDICATOR Filed Feb. 10, 1956 _ .60 L 7 Sheets-Sheet 3 F/ g. 70 80 éwmhngj ZWH E é?nwhgj :m \Z MH MZ Y: Y W,. H;W Hg. 6b b w H. H _H 2 W a a m w 2 8‘“l 25:? u 2 m -Ywun.SA H I.8 8 9 0(\J ._JBw 1,.A m m mw 8 )0/0.10 6% 1m M ...J_ M N2 Wm 5% .mm wM__ .R April 30, 1963 3,088,062 A. A. HUDIMAC ELECTROMECHANICAL VIBRATORY FORCE SUPPRESSOR AND INDICATOR Filed Feb. 10, 1956 NOlSY 7 Sheets-Sheet 4 / 86 EH2 88 := F/g. 9b Fig. 90 Fig. /00 Hg. /00 /86 =: /24 “a2 [90 NOISY 0 ZWH MQ INVENTOR. ALBERT A. HUD/MAC BY 2 é . z. /’ ATTORNEYS April 30, 1963 A. A. HUDIMAC 3,088,062 ‘ ELECTROMECI-IANICAL VIBRATORY FORCE SUPPRESSOR AND INDICATOR Filed Feb. 10, 1956 v Sheets-Sheet 5 gr. K IgN ] (90 Q, Fig/l0 20 C?) ...j ( 5E ' ' l g. Fig. //b E INVENTOR. ALBERTA. HUD/MAC A TTOR/VEYS April 30, 1963 3,088,062 A. A. HUDlMAC ' ELECTROMECHANICAL VIBRATORY FORCE SUPPRESSOR AND INDICATOR 7 Sheets-Sheet 6 Filed Feb. 10, 1956 i | . 1_______.______________.___ TO TUNING INDICATOR A INVENTOR. ALBERT A. HUD/MAC BY '5 — I” A TTORNEYS United States Patent 0 3,@33,0?2 we IC€ f’a’rerrteel Apr. 39, 1953 2 1 tory force is manifested as the motion of one transducer part and its backing mass. 3?3§?62 ELECTROMECHANECAL VHBRATORY FORCE SUPPRESSGR AND lNDlCATQ/“R Albert A. Hudimac, 2720 Grandview, San Diego, Calif. Filed Feb. 10, 1956, Ser. No. 564,$35 iii Claims. (till. 318-428) (Granted under Title 35, US. Code (1952), see. 266) The external electrical im pedance, the terminal impedance of the transducer, may be speci?ed as a function of vibration frequency for a 5 transducer such that there results a combination of me‘ chanical and virtual mechanical elements which in one case may remain anti-resonant over a broad band of fre quencies. In a second case, wherein a machine is resili ently supported from a base, the terminal impedance is The invention described herein may be manufactured and used by or for the Government of the United States 10 so speci?ed as to effect a combination of mechanical and virtual mechanical elements which effectively reduces to of America for governmental purposes without the pay zero the dynamic stiffness of the resilient support where ment of any royalties thereon or therefor. by protection is afforded to the lowest frequencies Without This invention relates to the art which deals with vibra impairing the ability of the resilient support to sustain tory forces and more particularly to the indication of the the weight of the machine and withstand shock. 15 characteristics of vibratory forces and the control of The characteristics of the A.-C. current which flows vibration of broad frequency ranges and remote adjust through the transducer and its terminal impedance, and ment of frequency or frequencies of optimum suppression. also the velocity of the moving transducer part are di Motion of practically all types of bodies, machines and systems is invariably accompanied by vibration and noise. rectly proportional to the characteristics of the exciting The desirability of eliminating such vibration and noise 20 vibratory forces which may thus be measured by suitable current or velocity indicators. has long been recognized and much effort has been di Accordingly, it is an object of this invention to suppress rected toward the solution or" this problem. The problem vibration. is of particular gravity in submarine warfare where a ves Another object of this invention is the reduction of sel’s safety may depend upon the suppression of vibra tion and noise of the auxiliary equipment which is nor 25 radiated and self noise of a sea-going vessel caused by transmission of vibration of machines to the hull of the mally left in operation in ultra-quiet or patrol-quiet con vessel or the passage of the vessel through the Water. ditions. Still another object of this invention is the protection Mechanical anti-resonant systems comprising springs of sensitive or fragile equipment from vibration or shock and masses have been added at suitable places in a vi bratable mechanical system to produce a large mechani 30 transmitted from its base. A further object of this invention is the suppression of cal impedance at the frequency of anti-resonance of the vibration over board frequency ranges. added elements. Such an arrangement is effective only Another object of this invention is the remote control over a narrow ‘band of frequencies unless it is damped, of the frequency or frequencies of optimum vibration in which case its effectiveness at resonant frequency is re duced. Further, the resonant frequency is ?xed or at 35 suppression. least ‘difficult to adjust. Adjustment cannot be effected remotely. Another known solution is the interposition of resilient means between the element to be protected from vibra tion and the mechanical element in which the vibration produced force is generated or through which it is trans mitted. To work effectively the impedance of such resili ent means must be small compared to the impedance of Still another ‘object of this invention is the reduction of the dynamic stiffness of a resilient support without impairing the ability of the support to sustain a load and absorb shock. A further object of this invention is to maintain the mechanical impedance of a vibratable mechanical system at an extremely high value over a broad frequency range. Still another object of this invention is to maintain a the protected element or of the vibration transmitting 45 low impedance motion transmitting path in a vibrata-ble mechanical system down to as low a frequency as is de element. This requires either springs which are too soft sired. to support the protected machine or the restriction to A further object of this invention is the provision of high frequencies. a vibration suppressor having a structure which is sub The present invention is composed of electrical and stantially independent of the physical characteristics of mechanical elements having speci?ed properties and em the system in which vibration is to be suppressed. bodied in a design such that the electrical elements are Another object of this invention is to measure vibra transduced into virtual mechanical elements. Certain of tory forces. the electrical elements may be remotely located and ad Still another object of this invention is to indicate the justable to effect remote adjustment of virtual mechanical impedance thereof. Further, the electrical elements may 55 imbalance of a dynamic machine. Other objects and many of the attendant advantages be designed to provide electrical impedance which varies of this invention will be readily appreciated as the same with frequency variations of the exciting vibratory forces becomes better understood by reference to the following in such a manner as to maintain over a broad frequency detailed description when considered in connection with band a virtual mechanical impedance in the system which will produce optimum vibration suppression. More spe 60 the accompanying drawings wherein: FIGS. 1a and 1b show one form of the invention as ci?cally the invention comprises an electro-mechanical transducer which senses the force tending to create vibra tion of a machine or the base on which the machine is mounted. This exciting force is manifested as a voltage applied for the purpose of suppressing vibration of a noisy machine rigidly mounted on a base and the equiva lent mechanical circuit thereof; FIG. 2 is a sectional view of the transducer of FIG. 1a; generated by relative motion of two transducer parts 65 FIG. 3 is a sectional view of part of the structure of which causes a current to flow in a circuit including the transducer and an external electrical impedance. The FIG. 2; FIG. 4 is a circuit diagram of the electrical connec external impedance adjusts the phase and amplitude of of the current in such a manner as to cause this current tions of the transducer of FIG. 2; FIG. 5 is a modi?cation of FIG. 4; 70 posite to the exciting forces. Where neither the machine FIGS. 6a and 6b show another form of the invention nor its base is permitted to move transmission of the ‘as applied for the purpose of isolating an object resiliently to create forces in the transducer which are equal and op exciting energy to the system is prevented and the vibra 3,088,062 3 41. equal and opposite to the exciting forces tending to pro duce the vibration. In effect, the transducer, when properly terminated, presents an exceedingly great im pedance to the vibratory exciting forces and, furthermore, mounted on a noisy base and the equivalent mechanical circuit thereof; , FIGS. 7a—1lb inclusive show several additional forms of the invention as applied and the respective equivalent mechanical circuit diagrams thereof; FIG. 12 diagrammatically depicts the manner in which will do so over as Wide a frequency band as the terminal impedance corresponds to that speci?ed below. a number of transducers of this invention may be ar ranged to suppress vibration in three linear and three ro Analysis tational directions; The condition on the electrical termination is obtained FIG. 13 is a schematic diagram of one circuit which 10 by treating the linearized form for steady state harmonic provides a terminal impedance of the type speci?ed; oscillation. More complicated behavior can be obtained FIG. 14 is a schematic diagram of the invention modi by superposition of these results. ?ed for use as an indicator of vibratory forces; The D.-C. current flowing through the coils of the trans FIG. 15 shows another manner in which the inven ducer produces a flux, (#1, in the cores 16, 18 which can tion may be used as an indicator of vibratory forces; 15 be expressed as FIGS. 16 and 17 graphically indicate results obtainable ¢1=¢10+(a¢1/ag)Ag (1) with this invention; and provided the change in gap or incremental gap Width, Ag, FIG. 18 graphically indicates one type of optimum ter is small compared to the undisplaced gap, g0. Here on mination. In the drawings like reference characters refer to like 20 is the flux at equilibrium position and 6¢1/8g is slope of curve ¢1(g) at the equilibrium position. Thus, ¢1 has parts. a static component and an A.-C. component. There is As shown in FIG. la, a machine 10’ Which is “noisy” an additional A.-C. ?ux, 452, which is caused by the A.-C. or vibrates due to dynamic imbalance or other factors is current, ib circulating in the coils due to relative motion rigidly secured to a base 12 which may be, for example, of the two transducer parts. It is given by the hull plate of a vessel or a structural member secured thereto. In this case the source of noise might alterna tively be in the base and caused by vibration of other machines or passage of the vessel through the water. The vibration suppressor 14 comprises a variable reluc tance transducer having two U-shaped cores 16, 18 25 The ?ux creates a force of traction on the pole faces of the cores, given by (FIGS. 2, 3) of oriented grain ferromagnetic material, each wound with a number of turns of conductive wire 20, mounted in cups 22, 24, and impregnated with potting compound 26 which rigidi?es each core, coil and cup where A is area of each pole face, and where factor of 2 is used because there are two gaps. We shall assume assembly. Cup 24 is rigidly secured to base 12 while 35 that ¢1>>¢2. Then substituting from Equations 1 and 2 cup 22 is rigidly secured to a resilient circular plate 28‘ into 3, and neglecting second order, D.~C. and second which may be a stainless steel leaf spring rigidly mounted harmonic terms, we get to base 12 by means of symmetrically arranged studs 30 or the like and ?xedly carrying a backing mass or weight 32. Terminals 34 are provided for electrical connection 40 of the coils 20. p ‘The coils 20 of cores 16, 18 are connected in series This force represents a tension on or attraction between ‘each pair of pole faces. Hence, the coe?‘icient of Ag/Z aiding and excited with a D.-C. currentfed from battery 1n the first term on the right represents a pseudo stiffness, 36 (FIG. 4) through variable resistor 38 and a parallel s’. Because all terms except apl/ag are positive, the co tuned circuit comprising capacitor 40 and inductance 42. 45 efficient The tuned circuit, tuned to vibration frequency, is used to prevent shorting through battery 36 of the A.-'C. volt-j age generated in the coils during operation of the vibra [4510f 5451/59) 7rA tion suppressor while a voltage across resistor 38 is con herein designated as s’ represents a negative stiffness. A veniently used to supply a tuning indicator ‘(not shown). 50 real spring with stiffness s>s' is necessary to maintain a The described circuit provides a DC. magnetic bias. stable undisplaced gap go. The total tension on each core then is The series connected coils 20 are electrically terminated into a variable electrical impedance 44 to be described hereinafter. An alternative arrangement shown in FIG. 5 shunts 55 the A.-C. voltage of coils 20 across battery 36' by means The force FT is balanced at each core by forces or of capacitor 46 and the coils are coupled with the ter reactions peculiar to that core. At the core ‘13 fastened minal impedance 44’ through a transformer 48. In both to the base, the force FT is balanced against the open arrangements the magnetic bias may be alternatively pro circuit force of the machine, FF , and the reaction or inertia vided by permanent polarization of the cores, thus elimi due to the internal mechanical impedance of the machine, nating the D.-C. source and tuned rejection ?lter or the Z1, and to the mechanical impedance of the base and parts latter may be made broad band. ?xed'thereto, zb. The open circuit force of the machine The described transducer performs two functions si is the force the vibrating machine would exert on an multaneously. First it “senses” the exciting vibratory in?nitely rigid’foundation. Hence, forces which tend to create vibration of the base 12 and, 65 machine 10 and which are manifested as relative motion FT=_vb(Zi+Zb)+5E (6) of the two parts of the transducer and an A.-C. voltage where vb is the velocity of the base and of the machine generated thereby. This voltage ‘produces an A.-C. cur and the positive sense of g, vb (and later, of v,,) being rent which flows in a loop through the transducer coils taken from the transducer toward the base. In core 16, and through the external electrical impedance. The ex 70 the force of PT is balanced by the reaction due to the ternal electrical impedance adjusts the magnitude and mechanical impedance of the core and the mechanical phase of the current. The second function is the trans lmpedance z,, of its backing mass 32. Hence, duction of the adjusted current into suppressing forces whereby the transducer creates forces (and applies them to the vibrata'ble body, the base and machine) which are FTzvazb where Iva is the velocity of mass 32 and core 16. (7) 8,088,062 5. 6 In this case z, can be considered as impedance of a ma 1 The change in flux, caused by change in gap and by the be induced; it is given by chine, which replaces the backing mass and is to be pro tected from forces transmitted through the base. Since G is a positive number, it is necessary for either case that ‘Where E is in volts, ¢ is in gauss, and N is the number of turns on the cores. Substitution from Equations 1 (Ze+ZT) be purely reactive. This requires that the transducer and terminating impedance be lossless. The case of lossy elements will be considered below. It should be emphasized that vibration suppression of base circulating current in the transducer, causes a voltage to or of the backing mass is obtained for as wide a band 10 of frequencies as Equations 12 or 13, respectively, hold. Further insight can be obtained into the conditions for the suppression of oscillations by considering the equiva lent mechanical circuit of FIG. 1b. Only the case forv the suppression of the vibration of the base is given here. neglected. Note that E is taken positive in same direction as ib. Completing the circuit with load Ze, the voltage 15 The case for suppression of vibration of the backing mass or an isolated object substituted therefor is very similar. drop across the load being equal to the induced voltage, Solving simultaneous Equations 11 for vb gives where terms of second order or of second harmonic are E=Zeib (10) where Ze is the impedance of the electrical termination 20 44 or 44' of the transducer. The coef?cient of (—]'wib) in Equation 9 is the self inductance of the transducer. An actual transducer will also have an A.-C. resistance, RT, due to windings, eddy currents and hysteresis, and also distributed capacitance. For this reason the coet?cient is replaced by ZT, the 25 The total impedance, z into which the “open circuit force” blocked electrical impedance of the transducer. The blocked impedance may be de?ned as the impedance with drives is both A.-C. rand D.-C. current ?owing and the gap held (ZT+ZG)ZJ ?xed. I ~s1 zT= jw41rNz(l9-§0i4) +RT ( 10a) (15) We now have three simultaneous Equations in 6, 7, and 10. The desired independent variables are va, vb and i,,. We therefore express Q¥— _. - _g?:?Q dt -2(11b 0,), Ag-- jw (5T+Ze)[_j£§_:—s/)+Zn]'i‘G 30 Note that if the denominator of the last term is Zero, i.e., tzi~+ze>[—j(i?ll+ai+e=o (11) then z is in?nite. (12) Since 3’ is ?nite, W1, must be zero, as was demonstrated in the previous paragraph. Equation Equations 6, 7, 4, 10 then become: 15 can be rewritten 45 Clearly, z is composed of three impedances in series: Z1, zb and a parallel combination with an impedance of za in one branch, and in the other a series arrangement of impedance 50 Equations 11a, 11b and 110 can be written anaizaia i as shown in the equivalent circuit of FIG. lb. It will be O noted that the condition given by Equation 12 is the condi llziazzazs 11b = 35 tion that the parallel element is anti-resonant. Stated 55 (13111321133 vs 0 otherwise, the condition that vb=zero is satis?ed by mak ing the mechanical reactance za equal and opposite to The condition that vb be zero is that the complementary the mechanical reactance 60 G/ZTHH; (J) The impedance of the parallel branch in FIG. 1b is in ?nite at anti-resonance if the elements are not lossy. provided that the determinant of the matrix is not Zero. practice, this is not possible. G. a positive number, is herein termed the electrome chanical coupling constant. The impedance J In Let 65 where R=the resistance RT of the actual transducer plus the real component of Z2 and X =the reactive components of Z; and Ze. Then, (0 is herein de?ned as the effective mechanical capacitative G L .G GR impedance of the transducer, conveniently designated as 70 Z,+ZT*_JX+F (17) XCT. In like manner, the condition that va be zero is that the complementary minor of (123 be zero, i.e., provided, as is reasonable, that X>>R. Now the resist ance of the parallel circuit at anti-resonance, Rar is g0 (13) 75 [2312 (18) 1 3,088,062 p ' 0‘ I Under the condition that X>>R, GR; GR a through D.-C. blocking capacitor 78, is connected to the _@ a _.(s+s’) 2 TFWZTJFZJFG‘“ j w where use of condition (12) was made. _-_ Glad" Rar—‘-—_———,% R amps-A 2 other end of coils 20. It has been shown that the desired external impedance (19) G Hence, (20) where za=jwMw the impedance of mass 32. Since both terms on the right are the negative of real impedances, it and Equation 16 becomes 10 is clear that Ze is a negative impedance. An important class of negative impedance is obtained Z=Zi+Zb+Rar (21) by employing positive feedback in an ampli?er. A species Thus, it is seen that in order to make Rar large, Z8 and G of this class is the series type shown in FIG. 13 which is OJ should be large, R should be as small as possible and so connected that the current i ?owing through the circuit 15 (and through coils 20‘) as a whole ?ows through the ampli ?er input 49 in series with the ampli?er output. The phases are such (with an even number of stages) that the should be small. This last requirement implies that the resonant frequency of the transducer, f,,,, be near the fre ampli?er output tends to increase the current i, and thus quency range in which suppression is desired. It can be shown that these conditions also result in a small circulat ing current, ib, and velocity v,,. This is desirable because to retain linear operation 2}, must be a small fraction of the D.-C. bias current and the displacement must be a small fraction of go. Furthermore, since R=RT plus the 25 real component of Ze, R becomes small and RM large when RZe is negative and approaches RT in magnitude. positive feedback is realized. The negative feedback within the ampli?er 60 effected by elements 70, 72, en sures stability of the total negative impedance. If the ampli?er have a gain A and output impedance R, and the voltage applied across terminals 74, 76 be E, the summation of voltages around the series loop gives E=iZ3+iR1—iAZ3 (22) where Z3 is the impedance of the input 49. Thus, It is apparent that the electrical impedances speci?ed above require the use of negative inductances and/ or nega E/z'=Ze=Z3(1—A)+R1 tive capacitances in order to provide impedances which vary with frequency in accordance with Equation 12 or If A is greater than one the ?rst term on the right is a 13. negative impedance. To determine the value of this nega tive impedance Z3, for given parameters A and R1, it is only necessary to equate the values of Z,a from Equation Such elements do not exist in nature but circuits us ing negative resistance do exist for obtaining such ele ments. Such circuits are discussed on page 187 of B'ode’s “Network Analysis and Feedback Design,” published in 1951 by Van Nostrand. Negative resistance has been (23) 12 and 23 ' 35 thoroughly studied and a number of such well known cir cuits are described E. W. Harold in “Negative Resistance and Devices for Obtaining It,” Proc. I.R.E., vol. 23, No. =10, October 1935, page 1201. 40 However, it will be readily appreciated that the inven where L=G/s+s' and C=Ma/G. From Equation 25 it tion described herein will eifectively suppress vibration in is seen that the circuit whose impedance is Z3 comprises a narrow frequency band When the transducer is electrical the elements shown within the dotted box 49 where re ly terminated in a real, ?xed impedance component which sistor 50 has a value RT/A~1, resistor 52 is R1/A--1, in has a value determined in accordance with the stated de sign criteria at the particular frequency of interest. Fur 4:5 ductor 54 is LT/A—1, capacitor 56 is C/A-l and in z3-A——_1[R1+RT+JwLT+ “Maj/m0 ] (25> ductor 58 is L/A'-—-1. Thus the circuit of FIG. 13 having components as spec i?ed above comprises an impedance into which the trans suppression. The value of G can also be controlled re ducer may be terminated in order to effect optimum sup motely. Thus, for example, the vibration suppressor of this invention may be arranged to effect optimum sup 50 pression over a band of vibration frequencies of several octaves. With such termination the transducer of this pression at one predetermined vibration frequency. If invention in addition to its primary function of steady such frequency should for some reason vary from such state vibration or noise suppression, will largely prevent predetermined frequency the physical arrangement or motion of the base and machine due to shock or impulsive structure of the suppressor need not be changed. It is merely necessary to change the value of the terminal im 55 noise. This is true ‘by reason of the fact that shock comprises a broad band of vibration frequencies. When pedance, which may be a variable capacitor or inductance, at a remote location or to change the value of G by, for Z8 is such that broad band suppression is provided, then example, changing the magnetic bias. that portion of the shock induced motion which is due Since broad band vibration suppression is to be desired to those vibration frequencies within the broad suppres in many instances the terminal impedance 44 or 44' may 60 sion band is eliminated. In other words, the broad band take the form shown in the circuit of FIG. 13 which pro vibration suppressor of this invention is also a “shock absorber.” vides over a broad band an impedance Ze, looking from the transducer coils, of the nature speci?ed in Equations It is to be understood that the circuit of FIG. '13 is 12, 13. but one exemplary embodiment of a terminal impedance A series connected impedance 49 comprising resistors 65 which can meet the speci?ed conditions for a wide fre 50, 52, inductance 54 and capacitor inductor tank 56, 58 is quency range. Numerous other circuit arrangements connected to provide the input to a stable, even stage am which satisfy the conditions for terminal impedance may pli?er 64} (shown with two stages) comprising an electron be produced in accordance with the stated principles. discharge tube 62 (such as an ordinary vacuum triode) The curves of FIG. 16 indicate exemplary comparative resistance capacitance coupled through elements 64, 66 to 70 results which are obtainable with the vibration suppressor electron discharge tube 68. A negative feedback circuit of this invention. To obtain these curves the structure comprising resistor 70 and capactior 72 couples the plate and circuitry of FIGS. 1a and 4 are employed with a of tube 68 to the cathode of tube 612. Terminal 74 is mechanical shaker unit substituted for the noisy machine connected to one end of the series aiding transducer coils 10 and a velocity detector is secured to base 12. Curve A 230 while terminal 76, connected to the plate of tube 68 75 represents the values obtained with the transducer un thermore, the value of this terminal impedance can be con trolled remotely in order to vary the frequency of optimum 3,088,062 terminated (Ze==in?nity) but bias current ?owing and curve B represents values obtained with an optimum 10 low impedance path or mechanical “short circuit” is pro vided across impedance z,,. Such a low impedance path termination (for the resonant frequency of the system) is provided by series resonance in the shunt path which determined in accordance with the criteria stated above. The parallel LC circuit lid, 42 is tuned to the center of the band of frequencies used. As indicated in FIG. .16 occurs when the reactance a relative velocity suppression of ‘26 decibels is obtained at resonant frequency with the optimum termination, a J 0) equals reactance G/Ze+ZT. Thus, isolation is obtained when capacitor of 1.9 microfarads. There is a net suppression I of vibration over a band Width which is 11 percent of 10 z.= - zi+ GHQ-EL) central frequency while there is an increase in velocity of vibration outside of this band width with a constant The action of this type of suppressor may be explained electrical terminal impedance. as follows: The vibratory exciting force tends to vibrate At frequencies far removed from the resonant fre object 80 by exerting a force through real springs 82. quency only a few db in vibration supprwsion were ob 15 When a force is exerted across the springs there is rela tained. The reason can be seen with the aid of Equa tive motion between the two transducer parts which in tion 21. The quantity (Z1+Zb) is very large off reso duces a voltage in the coils thereof. Thus a current is nance, while R8,r at best is of the same order. This re caused to flow through the coils and the terminal imped sult demonstrates the need for careful application of the ance (not shown in FIG. 6a). If the termination is as design criteria discussed below Equation 2.1 if good vibra 20 speci?ed the resulting current has just the proper magni tion suppression is to be achieved. It is to be under stood that while the curves of FIG. 16 corroborate the results indicated by the equations set forth above they are merely indicative of results obtainable with a single tude and phase as to cause a force to be exerted by the core attached to the object 80 (and of course on the other core) which will exactly cancel the force of the springs on the object. The object thus has zero net force transducer in a limited situation and are not intended 25 acting upon it and so remains stationary. It will be seen to limit in any way the scope of the application of this that the arrangement of FIG. 6a with the speci?ed ter invention to other situations. mination effectively reduces, and even entirely removes Good vibration suppression is obtained at frequencies over a wide band of frequencies, the dynamic stiffness other than resonant frequencies. FIG. 17 shows the of springs '82 which support object '80. However, the relation between relative suppression of vibration velocity ability of the springs to support a heavy object and to and frequency in a single case. The plot shows that vi withstand shock remains unimpaired. bration suppression is best at resonant frequencies where In the arrangement of FIG. 6a, a lossy transducer does (z1+zb) is small, that suppression increases at the reso not prevent reduction of the dynamic stiffness to Zero but nant frequency, ;f,, of the transducer, and that it is sig does replace such stiffness with a resistance Rs given ap ni?cant throughout the frequency band, from 100v to 350 35 proximately by cycles per second. FIG. 18 shows the relation between values of the ter minating capacitor for optimum vibration suppression and R,= R/G(S ‘of > frequency for the single case of FIG. 17. The two ter and thus it is seen that G should be large and R small minal network of FIG. 13 may substantially fit this curve 40 to make Rs small. and thus the vibration suppression indicated in FIG. 17 ‘From FIG. 612 it can be seen that vibration of the base may be achieved over a wide band of frequencies. The 84, and of any device rigidly secured thereto is prevented curve of FIG. 18 is the value of a terminating capacitor when vb is zero, a condition which occurs when an in?nite calculated from Equation 12 and from measured values impedance is provided by anti~resonance of the parallel 45 tank circuit. Therefore, the terminal impedance is speci of G and ZT for a particular transducer. An investigation of the conditions of electrical termina ?ed by equating za to the sum of G/Ze+ZT and tion of Equations l2, l3 reveals that the terminal imped ance Z6 is speci?ed solely as a function of the physical and electrical structure of the transducer and vibration frequency. There is no relation between Z8 and the phy Of course, with such termination, object 80 will vibrate. The structure and arrangement of the system shown in sical characteristics of the machine and base, the system in ‘which vibration is suppressed, providing only that the FIG. 7a is the same as that of FIG. 6a but in the former change in gap width remain small. Thus, one vibration the source of noise is object 80 which may be a noisy suppressor of this invention may be applied with equal machine. The equivalent mechanical circuit of the sys effectiveness to different mechanical systems with no 55 tem of FIG. 7a, shown in FIG. 7b, is substantially change of the suppressor required. Large variations in similar to that of FIG. 6b and '3’ still represents the ex amplitude of vibratory forces can be accommodated, for citing vibratory force which is now the open circuit force example, by varying the mass of weight 32. of the machine 80. The position of the impedances repre In the embodiment shown in FIG. 6a an object 180 to senting base and machine or object are interchanged in be isolated from vibration ‘and shock is mounted through 60 the equivalent circuit. Where the noisy machine is to be springs 82 on base “84 from or through which vibration prevented from vibrating the terminal impedance is speci and shock are transmitted. The two transducer parts ?ed by which may be identical to elements ‘16 through 26 of FIG. 2 and having the same electrical connections and circuitry of FIGS. 4 or 5 are respectively rigidly secured 65 Where transmission of vibration to the base is to be to object 80 and base ‘84. From the equivalent mechani prevented the terminal impedance is speci?ed by cal circuit of ‘FIG. 6b, where 3? is the open circuit force of the noisy base, zb is the impedance of the base 84, 1a is the impedance of object 80, s is the stiffness of springs to 82, s’ is the negative stiffness of the transducer and As shown in FIG. 8a and 921, the arrangement of ‘FIG. G/ZQ-I-ZT is an impedance introduced by the terminated 1:: can be utilized with a noisy machine ‘86 supported by transducer as speci?ed above, the operation of the sys springs 88 on a base 90 with the suppressor mounted on tem can be readily determined. For the desired condi either the machine (FIG. 8) or base (FIG. 9). In the tion of isolation of object 80, the velocity va thereof must be zero. This condition therefore obtains when a 75 mechanical equivalent'circuits of FIGS. 8b and 9b, Z1 is 11 3,088,062 the impedance of the machine 86, zEL is the impedance of mass 32, s is the stiffness of leaf spring 28 and sm is the 12; rotational exicting force and the phase and magnitude of the resultant linear suppressor forces are opposite and stiffness of springs 38. In either case the termination is the same as that speci?ed in Equation 12. With this ter mination it will be seen that an in?nite impedance is pre sented to the existing force when the transducer is mounted on the machine since the parallel tank circuit is equal to the exciting force in the one linear mode. Pair 14A would suppress linear vibration parallel to the X axis of FIG. 12 and rotational vibration about the Z azis. yPair 14B would suppress linear vibration parallel to the anti-resonant (FIG. 8b). Therefore, vibration of both machine 86 and base 9%)‘ is prevented. larly, pair 14C would suppress linear vibration parallel in series with the in?nite impedance of the tank circuit shown in FIG. 12 may be selected to suppress any sub combination of the possible vibrational modes. In recapitulation, it may be stated that the vibration suppressor described herein performs the fundamentally desired function of providing a vibratable mechanical system with an effective mechanical impedance which Z axis and rotational vibration about the Y axis. Simi to the Y axis and rotational vibration about the X axis. With the transducer mounted on the base the latter is 10 Obviously a suitable subcombination of the transducers while velocity of the machine is shunted across the base by springs 88. Therefore the base remains still and the machine behaves as if the springs 88‘ were mounted on an in?nitely rigid base. The arrangements of FIGS. 10a and 11a are respec tively the same as those of FIGS. 8a and 9a but the source of noise in the former is in the base. The termi nation remains as speci?ed in Equation 12. With the transducer attached to the machine (FIGS. 10a, 10b) an in?ite impedance is presented by the tank circuit to velocity of the machine while velocity of the base is shunted across the machine by springs 88. Here the base may vibrate but the machine is still. With the trans ducer attached to the noisy base (FIGS. 11a, 11b) an in?ite impedance is presented to the exciting vibratory force by the anti-resonant tank circuit. Thus, as in the arrangement of FIG. 8a and of FIG. 1a vibration of both the machine and base is prevented by reason of the fact that no transfer of energy of the exciting force to the suppressed system is possible. While the analysis and description which appears above has been con?ned to a vibration suppressor embodying a variable reluctance transducer it will be readily appre ciated that the principles of the invention are equally ap plicable to other types of electromechanical transducers. For example, in the case of the moving coil type of trans ducer where the moving coil is used in place of one core may be maintained at an optimum value over a broad frequency range and may be remotely adjusted. De pending upon the particular system and the results de sired this function is performed in one of two ways. In one case there is provided in the system an extremely high mechanical impedance which prevents transfer of energy. Alternatively, there is provided an extremely low impedance series resonant motion transmitting path, down to frequencies as low as desired, which shunts the velocity of a part in which vibration is to be prevented. Measurement of Vibration As will be shown below each of the quantities ib, the adjusted A.-C. current ?owing through the transducer coils and the terminal impedance, and 11,, the velocity of one moving transducer part is directly proportional to the exciting vibratory force and the suppressor forces created by the transducer. Therefore, to measure the magnitude of the exciting force it is merely necessary to measure this current or velocity. Thus, to measure the open circuit ‘force, or imbalance of machine 10 of FIG. 1a, it is merely necessary to provide a suitable current indicating device and the ?eld structure in place of the other it can be such as the ammeter 100 shown in FIG. 14 in the trans demonstrated that the results are the same as for the 40 ducer coil circuit. Alternatively, as shown in FIG. 15, a variable reluctance transducer, except that the negative stiifness thereof, s’, is zero and the electromechanical coupling constant G is de?ned as G=B2l2>< 10*9 where B is ?ux density in the gap occupied by the moving conventional velocity detector 102, well known in the art, may be mounted on the moving transducer part or the mass 32 ?xed thereto. The reading of detector 102 or amrneter ‘100 is directly proportional to the exciting force 45 and the indicators may be so calibrated as to yield direct measurements of the unknown forces. It is to be under coil and l is total length of Wire of the moving coil in stood that FIGS. 14 ‘and 15 show circuits and structures the magnetic ?eld. which may be identical with those of FIGS. 4 and 1a re Similar analyses using lumped parameters could be spectively save for the addition of elements 100 and 102. made for still other types such as electrostatic, tangen 50 As will be readily ‘appreciated each of the embodiments tial variable reluctance and tangential electrostatic. A or ‘applications described herein may be modi?ed by addi— somewhat more complicated device using magnetostric tion of either ‘a current or velocity detector, or both, to 'tive or piezoelectric transducers could be used. In these provide apparatus for measuring vibratory forces. It will types the generated ‘forces, mass and stiffness are not be seen that in addition to the linear relation between lumped and hence analysis is more complicated, but the 55 magnitude of exciting forces and either current or velocity, basic principles still apply. there is a linear relation between the frequencies and In the discussion thus far, the forces treated have been phases thereof and these characteristics of the exciting unidirectional linear oscillations and they tend to give forces may be measured by measuring frequency and rise to unidirectional displacements. In the general case phase of current or velocity. For example, the ammeter of a rigid machine, there can be three mutually perpen 60 100 may be replaced with ‘a suitable frequency or phase dicular components of linear Vibration ‘and three mutually detector or the latter may be provided in addition to the perpendicular components of rotational vibration. To ammeter1 suppress vall such components would require six of the Analysis described suppressors 14, as diagrammatically illustrated in FIG. 12, which are arranged in three pairs, 114A, 14B, 65 When the external electrical termination of the trans and 14C with the pairs A, B, C being oriented mutually ducer is chosen so as to suppress vibration of the base, the perpendicular to each other. Thus the transducers of open circuit force, 3? is effectively transferred to the total one pair, with axes of vibration (or linear vibration sup backing mass. This can be seen by noting that, when the velocity of the base is zero, the forces produced by the would take care of ‘one linear and one rotational mode of 70 transducer cancel the force in the machine. This bucking vibration, when the magnitude, phase and points of ap force is obtained in part from the traction on the base plication of the suppressor forces created by the trans ‘core and‘ in part due to the strain on the (dynamic) ducers of such pair are such that the moment of force spring. The traction on the backing mass core is equal exerted by the pair of suppressor forces is equal to the and opposite to that on the base core; the reaction of the rotational moment of the particular mode of vibratory 75 (dynamic) spring on the backing mass is opposite to its pression) parallel and separated by a suitable distance 3,088,062 13 14 said transducer remains high over a broad band of fre reaction on the base. Hence the forces exerted on the total backing mass are opposite to the bucking forces. quencies. 3. The structure of claim 1 wherein said circuit means Since the bucking forces are equal and opposite to the open-circuit force of the machine, the force on the backing mass is equal to the open~circuit force. includes means for varying said electrical impedance with frequency in accordance with the tendency of said mechanical impedance to vary with the frequency where This can be proved rigorously by solving Equations 11a, 11b, 1110 for v9‘ and then imposing the condition for vb-_—‘0, i.e., Equation 12. The result is by the mechanical impedance of said transducer remains high over a broad band of frequencies. 4. A transducer comprising a pair of cores of magnetic 10 material, a coil on each core, spring means resiliently interconnecting said cores, means for energizing said coils Clearly, then, if the total backing mass is known, and if v9, ‘for the condition vb=0 is known, 3“ is given by the product of these two values, i.e. in series aiding to provide a steady magnetic bias, and electrical circuit means connected with said coils for pro viding said transducer with a low effective mechanical 15 When the external electrical termination of the trans impedance. 5. The structure of claim 4 wherein said circuit means includes means for providing a negative electrical imped ducer is chosen so as to suppress the vibration of the base, ance in said circuit. 6. The structure of claim 4 including means in said transducer and the external electrical termination is of such a magnitude and phase that it creates a force in the 20 circuit for varying the electrical impedance thereof in accordance with the tendency of said mechanical imped transducer to buck out the open circuit force. ance to vary with frequency. If Equations 11a, 11b, ‘and 110 are solved for ib and 7. A transducer comprising a pair of cores of magnetic then the condition for vb=0 are imposed (i.e., Equation material, a coil on each core, spring means resiliently 12), the result is interconnecting said cores, means for energizing said coils the current circulation through the loop formed .by the ,-b =5cZZL><_1.Qi?¢_I/9l ( Ze+ ZT ) Zn 25 in series aiding to produce a steady magnetic bias, and electrical circuit means connected with said coils, said circuit means having an electrical impedance which e?ec But by Equation 12 tively provides said transducer with a high mechanical 30 35 All of the quantities in the denominator on the right hand side can be determined. The current, ib, can be determined by measuring the voltage drop across a small resistor placed in series with the external electrical ter— mination such as the ammeter of FIG. 14. Note that the machine vibration of which is to be meas ured need not be placed on any particular test mount. impedance, said circuit means including means for indi cating the current therein. 8. A transducer comprising a pair of cores of magnetic material, a coil on each core, spring means resiliently interconnecting said cores, means for energizing said coils in series aiding to produce a steady magnetic bias, elec trical circuit means connected with said coils, said circuit means having an electrical impedance which effectively provides said transducer with a high mechanical imped ance, and means for indicating the relative velocity of said cores. 9. The structure of claim 7 wherein said circuit means includes means for varying said electrical impedance with frequency in accordance with the tendency of said mechanical impedance to vary with the frequency where 45 by the mechanical impedance of said transducer remains high over a broad band of frequencies. 10. The structure of claim 8 wherein said circuit means includes means for varying said electrical impedance with Speci?cally, it can he “in situ,” i.e., in the place that the frequency in accordance with the tendency of said machine is actually used. Obviously many modi?cations and variations of the 50 mechanical impedance to vary with the frequency where by the mechanical impedance of said transducer remains present invention are possible in the light of the above high over a broad band of frequencies. teachings. It is therefore to be understood that within the scope of the ‘appended claims the invention may be References Cited in the ?le of this patent practiced otherwise than as speci?cally described. What is claimed is: UNITED STATES PATENTS 55 l. A transducer comprising a pair of cores of magnetic material, a coil on each core, spring means resiliently interconnecting said cores, means for energizing said coils in series aiding to produce a steady magnetic bias, and electrical circuit means connected with said coils, said circuit means having an electrical impedance which once t-ively provides said transducer with a high mechanical impedance. 2. The structure of claim 1 wherein said electrical impedance is a negative impedance determined in accord 65 ance with the characteristics of the transducer and varies with frequency whereby the mechanical impedance of 1,535,527 1,535,538 1,997,423 2,136,219 2,226,571 2,302,219 2,484,022 Harrison _____________ __ Apr. 28, Max?eld _____________ __ Apr. 28, Loser _________________ __ Apr. 9, Scherbatskoy __________ __ Nov. 8, McG-oldrick __________ __ Dec. 31, Hostetler ____________ __ Nov. 17, Esval ________________ __ Oct. 11, 1925 1925 1935 1938 1940 1942 1949 2,660,062 Frowe _______________ __ Nov. 24, 1953 2,722,194 2,776,560 2,788,457 Hoffman ______________ __ Nov. 1, 1955 Erath _________________ __ Jan. 8, 1957 Griest ________________ __ Apr. 9, 1957

1/--страниц